In a swing arm of an exemplary motorcycle, the rear end portion of the swing arm supports the center portion of an axle (e.g., Patent Literature 1). In the swing arm in which the rear end portion supports the center portion of the axle, the axle is rotatable with respect to the swing arm, and a wheel hub is mounted on the axle in such a manner that the wheel hub is rotatable together with the axle.
In the rear wheel portion of an exemplary motorcycle, a sprocket around which a chain for transmission of driving power is coupled to an axle via a damper. In the above-described swing arm in which the rear end portion supports the center portion of the axle, a first coupling member (sprocket member) around which the chain is wrapped is relatively rotatable with respect to the axle, and a convex portion formed on the side surface of a second coupling member which is spline-coupled to the axle is fitted into a recess formed on the side surface of the first coupling member via a damper member.